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  • Title: The cytochrome c peroxidase activity of cytochrome oxidase.
    Author: Orii Y.
    Journal: J Biol Chem; 1982 Aug 25; 257(16):9246-8. PubMed ID: 6286608.
    Abstract:
    I have found that mammalian cytochrome oxidase catalyzes the peroxidatic oxidation of ferrocytochrome c under strictly anaerobic conditions. An apparent Km value for ferrocytochrome c was 2 microM, and a second order rate constant, estimated as an extrapolated value, was 1.4 X 10(6) M-1 s-1 at pH 7.4 at 25 degrees C. These values were quite similar to the corresponding values of 6.4 microM and 1.9 X 10(6) M-1 s-1 determined for the intrinsic oxidase activity. The rate of the peroxidatic oxidation showed a hyperbolic dependence on the concentration of hydrogen peroxide, and the apparent Km value ws 0.18 mM. Cyanide and azide at 0.1 mM inhibited the peroxidase activity by 100 and 98%, respectively, whereas, under carbon monoxide at 750 mm Hg, 10% of the activity still remained. Under air, cytochrome oxidase acted simultaneously as oxidase and peroxidase.
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